Professor Daniela Bortoletto

Abstract:

The MALTA family of Depleted Monolithic Active Pixel Sensors (DMAPS) is produced using Tower 180 nm CMOS technology, specifically targeting radiation-hard applications in the HL-LHC and beyond. Several process modifications have resulted in radiation hardness up to 3 × 1015 1 MeV neq/cm2 and time resolution below 2 ns, with uniform charge collection efficiency across the chip formed of 512 × 224 pixels with a size of 36.4 × 36.4 μm2. This is achieved when adopting high-resistivity Czochralski substrates with backside metallisation to obtain a good propagation of the bias voltage. This contribution will show the most recent results obtained on MALTA2 chip demonstrators, including signal efficiency, noise occupancy and time resolution, at different levels of irradiation as well as the performance of the MALTA telescope permanently installed at the SPS at CERN and used in the test beam campaign in 2021-2023.

Abstract:

The ATLAS trigger system is a crucial component of the ATLAS experiment at the LHC. It is responsible for selecting events in line with the ATLAS physics programme. This paper presents an overview of the changes to the trigger and data acquisition system during the second long shutdown of the LHC, and shows the performance of the trigger system and its components in the proton-proton collisions during the 2022 commissioning period as well as its expected performance in proton-proton and heavy-ion collisions for the remainder of the third LHC data-taking period (2022–2025).

Abstract:

Inelastic beam-gas collisions at the Large Hadron Collider (LHC), within a few hundred metres of the ATLAS experiment, are known to give the dominant contribution to beam backgrounds. These are monitored by ATLAS with a dedicated Beam Conditions Monitor (BCM) and with the rate of fake jets in the calorimeters. These two methods are complementary since the BCM probes backgrounds just around the beam pipe while fake jets are observed at radii of up to several metres. In order to quantify the correlation between the residual gas density in the LHC beam vacuum and the experimental backgrounds recorded by ATLAS, several dedicated tests were performed during LHC Run 2. Local pressure bumps, with a gas density several orders of magnitude higher than during normal operation, were introduced at different locations. The changes of beam-related backgrounds, seen in ATLAS, are correlated with the local pressure variation. In addition the rates of beam-gas events are estimated from the pressure measurements and pressure bump profiles obtained from calculations. Using these rates, the efficiency of the ATLAS beam background monitors to detect beam-gas events is derived as a function of distance from the interaction point. These efficiencies and characteristic distributions of fake jets from the beam backgrounds are found to be in good agreement with results of beam-gas simulations performed with the Fluka Monte Carlo programme.